Shares of Boeing Co. BA, +2.60% sank 5.1% in premarket trade, to lead all 30 Dow Jones Industrial Average DJIA, +1.65% components in losses ahead of the open, as the aerospace giant bore the brunt of China's threats to impose tariffs on American exports, including airplanes. Boeing's stock price decline would shave about 117 points off the Dow's price, while Dow futures YMM8, -1.95% slumped about 519 points.